截取视频第一帧作为预览图片

截取视频第一帧作为预览图片

capture screen(function(){var video, output;var scale =0.8;var initialize =function() {output =document.getElementById("output");video =document.getElementById("video");video.addEventListener('loadeddata',captureImage);};var captureImage =function() {var canvas =document.createElement("canvas");            canvas.width = video.videoWidth * scale;            canvas.height = video.videoHeight * scale;            canvas.getContext('2d').drawImage(video,0,0, canvas.width, canvas.height);var img =document.createElement("img");            img.src = canvas.toDataURL("image/png");            output.appendChild(img);}; initialize();})();